Overhead projector



Jan. 16, 1968 G. ALTMAN 3,363,506

OVERHEAD PROJECTOR Filed Dec. 9, 1965 f MTCROSRHERE STRATUM n. METAL STRATUM PAPER SUBSTRATE METAL. STRATUM MICRQSRHERE STRATUM IMRRINT STRATUM M|cRoSRHERES HALE COATED APER SU BSTRATE A L l A A METALLIZED FIBRES REFRACTING MICROSPHERES COATED ON Fl ERES INVENTR. I Wm www ATTORNEYS E United States Patent O f' 3,363,506 OVERHEAD PRJECTOR Gerald Altman, 41 Westminster Road, Newton Center, Mass. 02159 Continuation-impart of application Ser. No. 249,351,

Jan. 4, 1963, and Ser. No. 349,853, Mar. 6, 1964. This application Dec. 9, 1965, Ser. No. 512,715

7 Claims. (Cl. 3S-24) ABSTRACT F THE DSCLSURE axis for deflection toward a viewing screen.

Background and brief description The present invention relates to optica-l projection and, more particularly, to a novel so-called overhead projector for graphic subjects of suihciently large size to be handled, viewed and marked during projection. In prior projectors of the foregoing type, handling, viewing and marking have involved various difiiculties. Thus, typically the source of illumination for projecting transparent copy is a large light box which may be unwieldy. And, typically the housing for opaque copy is fully enclosed so that manipulation and marking are inconvenient.

The present invention is a continuation-in-part of: U.S. patent application Ser. No. 249,351, filed Ian. 4, 1963, in the name of the applicant hereof for Optical Products, Processes and Devices, now U.S. Patent No. 3,269,839; and U.S. patent application Ser. No. 349,853, filed Mar. 6, 1964 in the name of the applicant hereof for System of Optical Projection of Images by Reflex Reliected Illumination, now U.S. Patent No. 3,222,986.

A primary object of the present invention is the provision of an overhead projector in which the housing comprises a lower platform of restricted vertical dimension, an upper casing for an illumination and optical system characterized by a transmitting-reiiecting means, and a post for supporting the casing above the platform a sufficient distance to provide manual and visual accessibility, so that substantially a single axis is established for light transmitted to and returned from; a directive reilector on the platform.

The overhead projector of the present invention is, for example, adapted for use with novel opaque copy in the form of a booklet or the like comprising a plurality of opaque sheets bound along one edge and having a reliex reiiecting stratum by which a representation associated therewith may be projected to a viewing screen by the optical system in the casing. In one form each such sheet incorporates a multiplicity of refracting microspheres in association with felted cellulosic bers of a paper sheet.

Other objects of the present invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the devices and products comprising the parts and components, which are exemplified in the following detailed disclosure, the scope of which will be indicated in the appended claims.

Brief description of drawing For a full understanding of the nature and objects of the present invention, reference should be had to the 3,363,506 Patented Jan. 16, 1968 FIGS. 3(a), (b) and (c) include exaggerated, -partly cross-sectional views, of reilex reflecting components for use in accordance with the present invention;

FIG. 4 is an isometric View of a booklet embodying the present invention; and

FIG. 5 is an isometric View of another booklet embodying the present invention.

Detailed description Generally, the overhead projector of FIGS. l and 2 comprises a lower platform 10, an upper casing 12 and a post i4 by which the upper casing is mounted above the lower platform. The lower extremity of post 14 is fixed within a seat i6 at an edge of platform itl. Casing 12 is adjustably fixed to post 14 by a collar 18 and by an associated tightening screw 20, which is turned through a threaded opening (not shown) in the collar under the control of a manually adjustable knob 20. The height of casing 12 above platform lll thus may be set at will. As shown, platform 10 generally is of at rectangular shape, the vertical dimension being much less in magnitude than either the longitudinal or the transverse dimension. Platform iii thus may rest on a desk or the like relatively unobtrusively. Casting i2, which generally is in the form of an inverted box, is composed of a sheet metal hood 2i? that is open at its lower and forward faces 22, 24.

The illuminating and imaging components of the overhead projector of FIGS. 1 and 2 are mounted on a bracket 26 and enclosed partially by hood 2l). The illumination source is an incandescent filament, electric lamp 28, rearwardly of which is a curved focusing mirror 30 and forwardly of which is a pair of condensing lenses 32, 34. The imaging components include a beam splitter 36 and an objective lens 38. Beam splitter 36 has a rearward face in the form of a Fresnel prism 40 by which horizontal collimated rays from source 28 are redirected vertically through objective lens 38 toward lower portion lt) of the housing. The conformation of Fresnel prism 40 is such as to include a multiplicity of mirror facets at an angle at 45 with respect to the axis of condensing lens 32, 34, and a multiplicity of horizontal facets which are optically clear. The forward face 42 of beam splitter 36 is provided with a thin iilm of alternately high and low dielectric strata that eiiiciently transmit the collimated light to the subject from source 28 and reflect collimated light from the Subject to a viewing screen.

Platform 1l) is provided with an upper panel 44, a lower panel 46, a rear panel 48, a forward panel 50, a right panel 52 and a left panel 54. Mounted lfor reciprocal vertical movement Within lower casing 10 is a support 56. Upper panel 44 has a cut-out 62 Which extends from a rim 58 at the right through an edge 6l) at the left. Left panel 54 is provided with a cut-out 64 which is a continuation of cut-out 62. It will be observed that a stack 66 of sheets or pages, when placed upon support 56 is capable of overlapping edge 60 and at the same time is capable of permitting support 56 to be depressed into platform 1l). Upward movement of support 56 is effected under the bias of a suitable leaf spring 68 and is limited by flanges 70, 72, which abut against the underside of upper panel 44 at forward and rearward edges of cutout 62. A pivotal retainer 74 at the rearward edge of cut-out 62 is movable between an opened position which permits support 56 to move into its uppermost position (notwithstanding the presence of stack 66 thereon) and a closed position which forces the uppermost face ot stack 66 into the focal plane of objective lens 33 (against the bias of spring 68). The parallelism of support 56 is maintained by pairs of links 76, '78 at opposite edges of support 56.

As shown in FIG. 2, stack of sheets 66 is in the form of a booklet, one of the edges of which is gummed as at Si) in order to permit maintenance of the sheets in a biock until used but to permit separation of the sheets one-by-one from the block during use. Preferred forms of the sheets of stack 66 are shown in FlG. 3. FIG. 3(a) shows a paper substrate 82, on opposite faces of which are reliective metallic coatings 84, S6. On the outer faces of metallic coatings 84, 86 are strata S8, 943 of refracting microspheres. At the outer faces of microsphere strata SS, 90 are suitable imprints 92, 94 of pencil, crayon or ink. An alternative structure is shown in FIG. 3(b) as incorporating a microsphere stratum 96 directly upon a base stratum 98, microsphere stratum 96 including microspheres, the surface of each of which hemispherically is optically clear and hemispherically is coated with an inner metallic reflector and an outer pigment. In FlG. 5(6), the half-coated microspheres may be deposited as a result of electrostatic attraction, which may be generated in paper substrate 9S by any suitable means. Such reliex reflecting strata are disclosed in: U.S. Patent No. 2,997,403, issued Aug. 22, 1961 in the name of Charles E. Seright for Reflex Reflective Coating Composition; and U.S. Patent No. 2,963,378, issued Dec. 6, 1960 in the name of Philip V. Palmquist for Glass Beads Hemispherically Reflectorized With Metallic Coating and Composition Thereof. An alternative reflex reflecting sheet is shown in FlG. 3(c) as having individual fibers at 100 each having an inner coating of a metal such as aluminum or silver 102 and an outer coating of refracting microspheres. The arrangement is such that almost one hundred percent of the cross-sectional area of the sheet is provided with reliex reflecting increments. It will be understood that alternative reex rellecting strata, for example metalized cube corners or the like, alternatively are associable with subject matter inthe overhead projector of FIGS. 1 and 2.

ln operation, light from source 23 is transmitted through beam splitter 36 and lens 38 to uppermost sheet 66 and is returned by the reflex reflecting elements of uppermost sheet 66 through lens 38 for reection -by beam splitter 36. In the illustrated overhead projector, a high efficiency polarizing plate 41 serves to convert a large proportion of the light to polarized form and forward face 42 of beam splitter 26 reilects or transmits depending on the polarization orientation of incident light. In addition, a quarter wave retardation plate 43 is positioned at lens 3S in order to produce and analyze circular polarization in the downwardly directed beam and the upwardly directed beam, respectively. The reversal in direction of circular polarization upon reection at uppermost sheet 66, which is non-depolarizing, enables eflicient rellection by the beam splitter of the light which it originally transmitted. Polarizer 41 may have any of a variety of compositions, one such composition being described in U.S. Patent No. 3,213,753, issued Oct. 26, 1965 in the name of Howard G. Rogers for Multilayer Lenticular Light Polarizing Device. Casing 12 is provided with suitable vents 43 for convection cooling as shown in U.S. Patent No. 3,207,031, issued Sept. 21, 1965, to R. Boggild et al. Beam splitter is of the socalled pile-of-plates type described in U.S. Patent No. 2,403,731, issued Iuly 9, 1946, in the name of Stephen M. MacNeille for Beam Splitter. Also, certain of sheets 66 are in the form of transparent plastic upon which notations or the like are printed or may be crayoned, such transparent sheets serving as overlaps for a variety of display purposes.

FIGS. 4 and 5 illustrate booklets embodying the present invention. The booklet of FlG. 4 is shown as comprising a series of pages, coated as in FlG. 3, and provided with a Ihalftone picture iti-i and lines of alphanumeric print 136. The pages are bound together by a spiral wire 10S, which is threaded through a series of holes in the pages. FIG. 5 illustrates a book having pages 112, coated as in FIGS. 3(51), (b) or (c), which are imprinted with pictures and characters, analogous to picture 104 and characters 106 of FIG. 4. The book of FIG. 5, which is sewn and bound at 168 and has a hard cover at 11), to all appearances is an ordinary book capable of being stacked on the shelf of a conventional library.

Conclusion The present invention thus provides a variety of overhead projection devices and products by which opaque or transparent subject matter may be brightly imaged. Since certain changes may be made in the foregoing disclosure without departing from the scope of the invention herein, it is intended that all matter contained in the above description or shown in the accompanying drawings be interpreted in an illustrative and not in a limiting sense.

What is claimed is:

1. An overhead projector comprising generaily flat, generally horizontal base means, support means upstanding from said base means, casing means positioned above and remote from said base means on said support means, illumination means in said casing means for directing a source beam of light toward a directive reflecting means at said base means, projection lens means mounted by said casing means for imaging a return beam of light from said directive reiecting means, and transmittingreiiecting means in said casing means for transmitting said source beam of light and for receiving said return beam of light substantially along a single axis, said transmitting-reflecting means deiiecting said return beam of light toward a viewing screen.

2. The overhead projector of claim 1 wherein said transmitting-reecting means is a polarizing beam splitting means.

3. The overhead projector of claim 1 wherein said directive reliecting means includes a specularly reflecting component. Y

4. The overhead projector of claim 1 wherein said directive reflecting means is a reilen reflecting means.

5. An overhead projector comprising generally tlat, generally horizontal base means, post means upstanding from an edge of said base means, casing means positioned above and remote from said base means on said post means, illumination means in said casing means for directing a source beam of light toward said base means, projection lens means in said casing means for imaging a return beam of light on a viewing screen, transmittingreflecting means in said casing means for transmitting said source beam of light and for receiving said return beam of light substantially along a single axis, said transmitting-reecting means deflecting said return beam of light toward said viewing screen, directively reflective stratum means upon said base means for carrying a presentation, said directively reflective stratum means having as a component a specular reflection means, and manually operable fastening means that enables said directively retiective stratum means to be aiixed readily to said base means and to be removed readily from said base means.

6. The overhead projector of claim S wherein said base means includes a support means movable with respect to said base means between an upper position and a lower position, and control means for locating said support means at an intermediate position depending upon the thickness of a stack of sheets thereon in order to maintain the uppermost sheet of said stacl; in the focal plane of said projection means.

7. An overhead projector comprising a generally flat, generally horizontal base platen, at least a post -upstanding from an edge of said platen, a casing positioned above and spaced from said platen on said post, a lamp in said casing for generating illumination Ifor said platen, a projection lens mounted by said casing for imaging illumination returned from' said platen on a -Viewing screen, and a transmitting-reecting means for transmitting said illumination generated by said lamp and `for receiving said illumination returned from said platen along substantially a single axis, said transmitting-reecting means deflecting said illumination returned from said platen toward said viewing screen, and a directive reilector means at said platen for bearing a representation for said imaging.

References Cited UNITED STATES PATENTS Blaisdell 88-24 Frost 88-26 Field 88-26 Frank et al. 88-24 Palmquist 91-1.5 Whittum 40-102 10 JOHN M. HORAN, Primary Examiner.

NORTON ANSHER, Examiner.

W. M. FRYE, Assistant Examiner. 

